Calculate the speed of a galaxy emitting light of wavelength

$$5.48 \times 10 ^ { - 7 } \mathrm { m }$$

which when received on Earth is measured to have a wavelength of

$$5.65 \times 10 ^ { - 7 } \mathrm { m }$$

.

Ultrasound of frequency 5.000 MHz reflected from red blood cells moving in an artery is found to show a frequency shift of 2.4 kHz. The speed of ultrasound in blood is

$$v = 1500 \mathrm { ms } ^ { - 1 }$$

. a. Explain why the appropriate formula for the frequency shift is

$$\frac { \Delta f } { f } = 2 \frac { u } { v }$$

, where u is the speed of the blood cells. b. Estimate the speed of the blood cells. c. In practice, a range of frequency shifts is observed. Explain this observation.

Determine whether a telescope with an objective lens of diameter 20 cm can resolve two objects a distance of 10 km away separated by 1 cm. (Assume we are using a wavelength of 600 nm.)

A distant galaxy emits light that has a wavelength of 434.1 nm. On earth, the wavelength of this light is measured to be 438.6 nm. (a) Decide whether this galaxy is approaching or receding from the earth. Give your reasoning. (b) Find the speed of the galaxy relative to the earth.

A sound wave of frequency 512 Hz is emitted by a stationary source toward an observer who is moving away at

$$12 \mathrm { ms } ^ { - 1 }$$

. a. Determine the frequency the observer measures. b. Calculate the wavelength of the sound as measured by i. the source and ii. the observer.

a. State what is meant by the Doppler effect. b. Illustrate the Doppler effect for the case of a moving source using wavefront diagrams. c. Outline one practical application of the Doppler effect. d. A disc of radius 0.20 m rotates about its axis making eight revolutions per second. Sound of frequency 2400 Hz is emitted in all directions from a source on the circumference of the disc. The sound is received by an observer far away from the disc. Determine the range of frequencies and the range of wavelengths that the observer measures.